1. Field of the Invention
The present invention generally relates to patterned recording media and a method of manufacturing the same, and more specifically to patterned recording media and a method of manufacturing the same using selective thermal coupling.
2. Description of the Related Art
In conventional magnetic recording systems, a written bit size is defined by the dimensions of the recording head. A written domain comprises several hundred magnetic grains. For example, for the highest recording density products being introduced in the market today (20 Gb/in2), the bit cell is about 620 nm×52 nm. To support such areal densities, the microstructure of the recording media has been engineered to consist of non-exchange coupled grains with grain diameters of about 10 nm. Therefore, a recorded domain involves about 400 grains.
Therefore, one approach to achieving higher recording densities is to reduce the bit size and consequently the media grain size. However, this approach is limited because at a critical grain volume, the magnetic grains become thermally unstable and spontaneously switch magnetization direction at normal operating temperatures due to superparamagnetism and are unable to maintain the magnetization orientation imposed on them during the writing process. In addition, as the number of grains is reduced, the noise arising from statistical fluctuations in grain positions or orientation increase.
Another approach to increasing recording density is to modify the microstructure of the media so that a bit is stored in a single grain, or a multiplicity of grains or magnetic clusters which are fully exchange coupled within the recorded bit dimensions. This approach, commonly referred to as “magnetic media patterning” requires that adjacent grains or clusters be magnetically isolated. This approach is perceived as a necessary means for extending magnetic recording to meet storage densities in excess of 100 Gb/in2.
Conventional methods of patterning magnetic media encompass a wide variety of techniques ranging from conventional lithography, to the use of particle and photon sources in combination with masks to produce patterned structures. For example. U.S. Pat. No. 6,168,845 to Fontana et al. (hereinafter “Fontana”) discloses a method of making patterned magnetic media using selective oxidation. The Fontana method includes depositing a layer of magnetic material on a substrate (e.g., a conventional nickel-phosphorus plated aluminum-magnesium substrate), covering portions of the magnetic layer with a protective mask that determines the patterning of the non-magnetic zones, and exposing the protective mask and the uncovered portions of the magnetic layer to an oxygen plasma. The oxygen plasma oxidizes the magnetic layer so that the uncovered portions have a reduced local magnetic moment. The result is a patterned magnetic medium with discrete magnetic and non-magnetic zones.
The utilization of ion beam implantation to achieve patterned media, has been disclosed in “Method for Spatially Modulating Magnetic Properties Using Ion Beam Implantation”, J. Baglin. E. E. Marinero and K. Rubin, (AM9-98-096).
Such conventional methods aim to significantly alter the magnetic properties of the regions exposed to the particles, energy sources, ions or reactive species. The areas of the magnetic material which were prevented from exposure by the mask, exhibit different magnetic properties from the exposed areas and information can be recorded and retrieved by taking advantages of the differences in magnetic properties between these two different material regions.
However, these methods have several drawbacks that inhibit their use in magnetic media manufacturing applications. For example, a storage density of over 100 Gb/in2 would require an exposure mask having a feature size of about 40 nm over large areas. In addition, the mask must be accurately aligned and positioned. Further, in the case of particle implantation and reactive ion etching, the mask may have a short lifetime because the impinging species are expected to be heated and deposited on the non-transmissive areas of the mask. In short, these methods generally require additional hardware and/or processing steps which result in higher fabrication costs and longer manufacturing cycle times.